Aerosol dispensers are generally well known in the art. These devices utilize transducers which generally create a spray of an active ingredient using a propellant. The resulting spray includes oversized liquid particles with a significant forward velocity which impact the surface or element being sprayed. The spray is non-uniform and results in a non-uniform deposition of active ingredient and consequent ineffective use of the active ingredient. There is no device which could deliver an aerosol having particles of a relatively small, uniformly consistent size. One type of aerosol dispenser presently in use is anti-asthmatic medication inhalers. In one such device, a 10-centimeter (4-inch) spacer was attached to the inhaler in an attempt to provide uniform particle size, which spacers produced a noncompact cumbersome inhaler. The transducer alone, however, is still ineffective to produce an aerosol having the desired characteristics.
U.S. Pat. No. 4,241,877 to Hughes shows a vortex generating device in FIGS. 5A, 5B, and 6, wherein a gas and a liquid pass into a flow passage together from an inlet. The mixture flows about a rod and forms vortices thereabout and enters a bore along a portion of the rod after which the mixture exits the device through a constricted bore to a semispherical diverging outlet. The liquid is partially atomized as it leaves the bore in the inlet and becomes fully atomized as it leaves the semispherical diverging outlet in a vortical gas stream. A device is also shown where a gas and liquid under pressure are supplied together through an inlet member to a transversely extending rod for formation of vortices. The vortices flow in a direction coaxial with the rod to a constricted outlet bore and to a semispherical diverging outlet. The vortices also flow along auxiliary passages toward the constricted bore portion to combine with the previously-mentioned coaxial flowing vortices.
The Hughes '877 device is suitable for relatively high mass flow rates, but would not be suitable for use with propellant-charged canisters containing a relatively low propellant-to-active-ingredient ratio. With such canisters, it is desirable to minimize the proportion of propellant in each shot while maximizing the concurrent output of the active ingredient. Furthermore, it would be relatively difficult and expensive to manufacture a device as indicated in the Hughes '877 patent and still provide the required aerosol characteristics in conjunction with the propellant-charged canister.
The present invention overcomes these deficiencies in the prior devices. The device provides an aerosol having particles which are uniform in size regardless of the variation in range of pressure provided through the propellant in the canister. This result inheres even with low propellant-to-active-ingredient ratios and low mass flow rates.
The present invention is useful in a number of applications where a relatively small concentration of propellant and active ingredient is used in applying the active ingredient. The invention may be utilized in aerosol medication inhalers, paint sprayers, topical medication applications, hairspray, deodorant, lubricants and other aerosol applications.
The present invention due to its unique operation on miniscule amounts of gas or liquified propellant permits a unique capability when used in conjunction with the apparatus disclosed in the copending applications CP&H Ser. No. 652,753 filed 9/18/84 and Ser. No. 555,703 filed 11/28/83 as a nebulizer permits operation at extremely low flow of oxygen or propellant namely from 0-5 liters per minute. This capability is of extreme importance in hospital and home therapy. Oxygen is toxic at high levels in 100% by volume concentration. Oxygen is also costly and at high levels makes for difficult patient ingestion of drugs.